Mixin improvements

Better handling of mixin call bodies, the `@content` item, and the
`content_exists` function.

Fixes #112.

Author: kaj

Diff for: CHANGELOG.md

@@ -7,6 +7,19 @@ The format is based on
 project adheres to
 [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Breaking changes
+
+* The `sass::Item::MixinCall` enum alternative was modified.
+
+### Improvements
+
+* Better handling of mixin call bodies, the `@content` item, and the
+  `content_exists` function.
+* Removed some debug printouts that was accidentally left in 0.21.0.
+
+
 ## Release 0.21.0 - 2021-06-01
 
 Progress: 3727 of 6171 tests passed in dart-sass compatibility mode.

Diff for: src/output/transform.rs

@@ -313,7 +313,7 @@ fn handle_item(
                     Mixin {
                         args: FormalArgs::none(),
                         scope,
-                        body: body.clone(),
+                        body: body.clone().unwrap_or_else(Mixin::no_body),
                     },
                 );
                 handle_body(
@@ -332,24 +332,18 @@ fn handle_item(
             }
         }
         Item::Content => {
-            if let Some(rule) = rule {
-                if let Some(content) =
-                    scope.get_mixin(&Name::from_static("%%BODY%%"))
-                {
-                    let sel = scope.get_selectors().clone();
-                    handle_body(
-                        &content.body,
-                        head,
-                        Some(rule),
-                        buf,
-                        ScopeRef::sub_selectors(content.scope, sel),
-                        file_context,
-                    )?;
-                }
-            } else {
-                return Err(Error::S(
-                    "@content not allowed in global context".into(),
-                ));
+            if let Some(content) =
+                scope.get_mixin(&Name::from_static("%%BODY%%"))
+            {
+                let sel = scope.get_selectors().clone();
+                handle_body(
+                    &content.body,
+                    head,
+                    rule,
+                    buf,
+                    ScopeRef::sub_selectors(content.scope, sel),
+                    file_context,
+                )?;
             }
         }
 

Diff for: src/parser/mod.rs

@@ -236,14 +236,7 @@ fn mixin_call2(input: Span) -> PResult<Item> {
         opt(body_block),
         terminated(opt_spacelike, opt(tag(";"))),
     )(input)?;
-    Ok((
-        input,
-        Item::MixinCall(
-            name,
-            args.unwrap_or_default(),
-            body.unwrap_or_default(),
-        ),
-    ))
+    Ok((input, Item::MixinCall(name, args.unwrap_or_default(), body)))
 }
 
 /// What follows an `@` sign
@@ -619,7 +612,7 @@ fn if_with_no_else() {
 fn test_mixin_call_noargs() {
     assert_eq!(
         check_parse!(mixin_call, b"@include foo;"),
-        Item::MixinCall("foo".to_string(), CallArgs::default(), vec![]),
+        Item::MixinCall("foo".to_string(), CallArgs::default(), None),
     )
 }
 
@@ -630,7 +623,7 @@ fn test_mixin_call_pos_args() {
         Item::MixinCall(
             "foo".to_string(),
             CallArgs::new(vec![(None, string("bar")), (None, string("baz"))]),
-            vec![],
+            None,
         ),
     )
 }
@@ -645,7 +638,7 @@ fn test_mixin_call_named_args() {
                 (Some("x".into()), string("bar")),
                 (Some("y".into()), string("baz")),
             ]),
-            vec![],
+            None,
         ),
     )
 }

Diff for: src/sass/functions/meta.rs

@@ -1,6 +1,6 @@
 use super::{check, get_opt_check, get_string, Error, FunctionMap};
 use crate::css::{CallArgs, Value};
-use crate::sass::Name;
+use crate::sass::{Mixin, Name};
 use crate::{Format, Scope, ScopeRef};
 
 pub fn create_module() -> Scope {
@@ -37,8 +37,14 @@ pub fn create_module() -> Scope {
         }
     });
     def!(f, content_exists(), |s| {
-        let content = s.get_mixin(&Name::from_static("%%BODY%%"));
-        Ok(content.map(|m| !m.body.is_empty()).unwrap_or(false).into())
+        let content = call_scope(s).get_mixin(&Name::from_static("%%BODY%%"));
+        if let Some(content) = content {
+            Ok((!Mixin::is_no_body(&content.body)).into())
+        } else {
+            Err(Error::error(
+                "content-exists() may only be called within a mixin",
+            ))
+        }
     });
     def!(f, feature_exists(feature), |s| {
         let (feature, _q) = get_string(s, "feature")?;

Diff for: src/sass/item.rs

@@ -42,7 +42,7 @@ pub enum Item {
     /// A `@mixin` directive, declaring a mixin.
     MixinDeclaration(String, FormalArgs, Vec<Item>),
     /// An `@include` directive, calling a mixin.
-    MixinCall(String, CallArgs, Vec<Item>),
+    MixinCall(String, CallArgs, Option<Vec<Item>>),
     /// An `@content` directive (in a mixin declaration).
     Content,
 

Diff for: src/sass/mixin.rs

@@ -1,4 +1,4 @@
-use crate::sass::{FormalArgs, Item};
+use crate::sass::{FormalArgs, Item, Value};
 use crate::ScopeRef;
 
 /// A mixin is a callable body of items.
@@ -11,3 +11,13 @@ pub struct Mixin {
     /// The body of this mixin.
     pub body: Vec<Item>,
 }
+
+impl Mixin {
+    /// An illegal mixin body, used for `@content` on mixin calls sans body.
+    pub(crate) fn no_body() -> Vec<Item> {
+        vec![Item::Property("%%NO-BODY%%".into(), Value::Null)]
+    }
+    pub(crate) fn is_no_body(body: &[Item]) -> bool {
+        body == [Item::Property("%%NO-BODY%%".into(), Value::Null)]
+    }
+}

Diff for: tests/spec/core_functions/meta/content_exists.rs

@@ -30,7 +30,6 @@ mod controls {
         );
     }
     #[test]
-    #[ignore] // wrong result
     fn test_true() {
         assert_eq!(
             runner().ok("// Regression test for sass/libsass#2842\
@@ -80,7 +79,7 @@ mod error {
         );
     }
     #[test]
-    #[ignore] // missing error
+    #[ignore] // wrong error
     fn in_function_called_by_mixin() {
         assert_eq!(
             runner().err(
@@ -103,7 +102,6 @@ mod error {
         );
     }
     #[test]
-    #[ignore] // missing error
     fn outside_mixin() {
         assert_eq!(
             runner().err("a {b: content-exists()}\n"),
@@ -144,7 +142,6 @@ mod test_false {
     use super::runner;
 
     #[test]
-    #[ignore] // unexepected error
     fn through_content() {
         assert_eq!(
             runner().ok("@mixin call-content {\
@@ -179,7 +176,6 @@ mod test_true {
     use super::runner;
 
     #[test]
-    #[ignore] // unexepected error
     fn empty() {
         assert_eq!(
             runner().ok("@mixin a {\
@@ -193,7 +189,6 @@ mod test_true {
         );
     }
     #[test]
-    #[ignore] // unexepected error
     fn non_empty() {
         assert_eq!(
             runner().ok("@mixin a {\

Diff for: tests/spec/libsass_closed_issues/issue_1640.rs

@@ -6,7 +6,6 @@ fn runner() -> crate::TestRunner {
 }
 
 #[test]
-#[ignore] // unexepected error
 fn test() {
     assert_eq!(
         runner().ok("@mixin foo() {\

Diff for: tests/spec/libsass_closed_issues/issue_1644/mixin_parent.rs

@@ -6,7 +6,7 @@ fn runner() -> crate::TestRunner {
 }
 
 #[test]
-#[ignore] // wrong error
+#[ignore] // missing error
 fn test() {
     assert_eq!(
         runner().err(